Air-pump.



V J. K. STEWART.

AIR PUMP.

APPLICATION FILED MAR 18. 1914.

Patented Oct. 26, 1915.

pur ne earns EN JQHN K. STEWART, OF CHICAGO, ILLINOIS, ASSIGNOR T STEWART-WARNER SPEED- GORPORATION, OF CHICAGO, ILLINOIS, A CORPORATION OF VIRGINIA.

AIR-PUMP.

Specification of Letters Patent.

Patented (lot. 26, 1915.

16 This invention relates to air compressors of the sort commonly installed on automo-,

biles for use in inflating tires and for furnishing compressed air for other purposes.

It consists particularly incertain improved means of lubrication and in features of arrangement designed to facilitate con- 'struction and assembly. These features are all described and illustrated'in the drawings, being particularly set out in theappended claims.

In the drawings :Figure 1 is a side elevation of a pump embodying this invention with certain parts broken away or shown in section, to disclose details of construction.

indicated by. the arrows 22 on Fig 1. Fig. 3 is a transverse detail section at line 33 on Fig. 1. Fig. 4 is a detail section taken as indicated at line 4-4 on Fig. 1. Fig. 5 is a perspective view of the crank case cover plate.

The pump shown in the drawings is of the single-cylinder type comprising essentially a cylinder, 1, provided with a snugly fitting piston, 2, which is connected by a pitman, 3, with the crank wrist, kl, of a crank shaft, 5, said shaft being provided with a slidably mounted gear, 6, adapted for operatively connecting the pump with any convenient prime mover, such as the engine or motor of a motor vehicle. The crank shaft, 5, is *journaied in a frame, 7, provided with a bracket, 8, which there is shown pivotally mounted a shifting lever, 9, whose forks, i? it, engage the gear, 6, for sliding it along the shaft, 5. Operative conietween the shaft, 5, and the gear, 6, hed by a cross pin, 11, in the shaft ging a slot, 12, in the elongated hub e gear, 6. The crank case, 13, is formed open at the bottom as indicated-in Fig. 2, in order that any excess of oil may be thus disposed of and not drawn into the pump cylinder so as to be expelled therefrom with Fig. 2 is a detail sectional View taken as egrally with the frame portion, 7, beingthe compressed air. This is particularly important when the air'is used for inflation of pneumatic tires of rubber, it being well known that rubber is injuriously affected by contact with lubricating oil. The lubrication of the crank shaft bearing is efi'ected through an oil hole provided with a common form of cap at 14, while the crank wrist is arranged to be supplied with oil through a hollow bent pin, 15, connecting with an oil hole, 16, in a boss, 17, which is formed on the cover plate, 18, of the crank case. This pin, 15, extends from the crank wrist alongside the bearing of the pitman, 3, and is accurately spaced therefrom by a washer, 19, so as to definitely position the pitman bearing on the crank wrist. Said crank wrist is provided with an oil duct, 20,-communicating with the bore of the hollow pin, 15, and the bent end of said pin being coaxial with the crank shaft, 5, is journaled in the boss, 17, so as to rotate with the crank shaft as an integral part thereof and forms a' continuous connection between the oil hole, 16, and the duct, 20, of the crank wrist.

The crank case, 13, being integral with the shaft bearing, 7, and not separable at any plane of the shaft axis is arranged to admit the crank shaft longitudinally through an opening in its end wall designed to be closed by the cover plate, 18; it will be understood that the crank shaft is entered with the crank arm, 21, extending upwardly as shown in Fig. 2, the pitman, 3, being then applied to the crank wrist, 4, and the pin, 15, being inserted in place, the cover plate, 18; is secured in position. The cylinder, 1, is formed with a flange, 22, which rests upon the top flange, 23, of the crank case, and the cylinder is centered in such position by means of a reduced portion, 24, fitting into a circular opening in the crank case flange. Four screws, 25, passing through holes in the crank case flange and taking into threaded openings in the flange, 22, serve to secure the cylinder in place. It will beunderstood that the piston, 2, is pivotally connected with the pitman, 3, by the customary wrist pin, not shown, and is inserted into the cylinder as the latter is fitted on to the crank case.

' Lubrication of the piston is effected through a circular wick, preferably formed of some non-combustible material as asbestos, and made in halves, 26, 26, embracing the cylinder just above the flange, 22.

a insane-o This Wick is provided with projections, 2?, extending into apertures in the cylinder Wall so as to Wipe the surface of the piston, 2, it passes them in its Working stroke. This 'Wick may he saturated with suliicient lubrieating oil to last for a considerable time, and With this method of lubrication the possibility of excessive oiling is reduced to a minimum, thus practically preventing the admixture of oil with the air expelled from the compression chamber. A flanged ring,

28,Wl1ih fits tightly over the flange, 22, is provided to retain the two halves, 26, 2b, of the Wick in place. i

The piston, 2, itself is made to control the air inlet which consists of a series of apertures, 29', formed in the piston wall .just above the lowest position of the end of said piston. The downward movement of the piston creates a partial vacuum in the cylinder which is satisfied by the inrush of air as the piston passes the ports, 29, near'the lower limit of its stroke, and the air thus introduced is expelled by the upward in oveinont of the piston, Preferably the ports, 29',

are surrounded with screen, 30, to exclude dust so far as possible.

In the upper end of the cyhnder there are formed two valve chambers, 31. and 32, pro-- vided, respectively, with ball valves, 33 and 34, and connected by a passage, on. These two valves are designed to supplement each other in case eitlser one of them should for any reason fail to seat perfect-ly thus insune ing the pump against loss of eiliciency through such cause. The chamber, 32, terminates as shown in a threaded nipple, 36, intended to receive the coupling of an. air hose or pipe for conducting away the air for use. As is usual, the cylinder walls are provided with radiating fins, 37, for dissipating the heat of compression.

I claim 1. In a pump a piston and a cylinder in which the piston is mounted to reciprocate, the cylinder Wall having at a plane trans-- verse to the piston movement and intermediate the ends of the piston path, an aperture leading through said wall and opening into the piston path, and an absorbent oil wick extending from the exterior of the cylinder through said aperture for wiping contact with the piston.

in con'ibination with a cylinder and a piston l'GClPI'OCiLlJlIlg therein, the cylinder havingat a plane transverse to the path of reciprocation of the piston intermediate the ends of said path a series of apertures leading from the outsidoof said cylinder to the path of the piston theccin, an annular oil wick of absorbent material encompassing the cylinder and having projections extending into said apertures for wiping contact with the piston, and means for retaining said annular wick in its position about the cylinder. In combination with a vertically reciprocating piston and a cylinder in which it is mounted to reciprocate, said cylinder having a series of lateral itl'lcl'tlllcs in its wall, an annular oil wick encircling" d cylinder and having; projections extending Ll'u'ough said apertures for wiping contact with the piston. p

in lin an air compressor a piston and an aperturcd cylinder in which it is mounted to reciprocate, an annular oil wick of absorbent non-combustible material encircling said cylinder and lowing a projection extending through the aperture thereof for wiping contact with the piston in its tinsel.

in combination with a. vertically"reciprocating piston, a cylinder in which it is mounted to reciprocate, said cylinder having a plurality of lateral apertures in its wall oncircling said cylinder and a wick having projections extending through said apcrtures for wiping contact with the piston in its travel, and an annular retaining wall on circling said wick.

In tcstinlony whereof I have hereunto set my hand at Chicago, Illinois, this 11th day of lllarch, 1914;.

JOHN H. STEWART. 

